ChemInform Abstract: Theoretical Study of Structural and Vibrational Properties of Al3N3, Ga3N3, and In3N3.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Computation of aromatic C3N4 networks and synthesis of the molecular precursor N(C3N3)3Cl6

The successful synthesis and structural characterization of molecules that represent segments of extended solids is a valuable strategy for learning metric and stereochemical characteristics of those solids. This approach has been useful in cases in which the solids are particularly difficult to crystallize and thus their atomic connectivity and overall structures become difficult to deduce with X-ray diffraction techniques. One such class of materials is the covalently linked C(x)N(y) extended solids, where molecular analogues remain largely absent. In particular, structures of C(3)N(4) solids are controversial. This report illustrates the utility of a simple molecule, N(C(3)N(3))(3)Cl(6), in answering the question of whether triazine based C(3)N(4) phases are layered or instead they adopt 3D structures. Here, we present density functional calculations that clearly demonstrate the lower stability of graphitic C(3)N(4) relative to 3D analogues.     

N, N, N′, N′-四丁基丙二酰胺萃取Pr3+的研究

利用丙二酸二乙酯与二正丁胺反应高收率的制备了N，N，N′，N′-四丁基丙二酰胺(TBMA)萃取剂。研究了硝酸浓度、硝酸锂浓度、萃取剂浓度以及温度等对萃取Pr(Ⅲ)分配比的影响，确定了萃合物的组成，得到了不同稀释剂中萃取反应的热力学数据。结合红外光谱和摩尔电导数据初步推断了萃合物的结构。     

Lanthanide Nitrido Borates with Six-Membered B3N6 Rings: Ln3B3N6

Metal compounds with heteroatomic ring systems of main group elements are a domain of coordination chemistry. However, lanthanide nitrido borates Ln₃B₃N₆ (Ln=La or Ce; see structure) are synthesized by the reaction of hexagonal boron nitride with LnN. The compounds contain the six-membered B₃N₆ ring, which can be seen as a fragment from one layer of the hexagonal BN structure.     

Enthalpies of formation of gas-phase N3, N3-, N5+, and N5- from Ab initio molecular orbital theory, stability predictions for N5(+)N3(-) and N5(+)N5(-), and experimental evidence for the instability of N5(+)N3(-)

Ab initio molecular orbital theory has been used to calculate accurate enthalpies of formation and adiabatic electron affinities or ionization potentials for N3, N3-, N5+, and N5- from total atomization energies. The calculated heats of formation of the gas-phase molecules/ions at 0 K are DeltaHf(N3(2Pi)) = 109.2, DeltaHf(N3-(1sigma+)) = 47.4, DeltaHf(N5-(1A1')) = 62.3, and DeltaHf(N5+(1A1)) = 353.3 kcal/mol with an estimated error bar of +/-1 kcal/mol. For comparison purposes, the error in the calculated bond energy for N2 is 0.72 kcal/mol. Born-Haber cycle calculations, using estimated lattice energies and the adiabatic ionization potentials of the anions and electron affinities of the cations, enable reliable stability predictions for the hypothetical N5(+)N3(-) and N5(+)N5(-) salts. The calculations show that neither salt can be stabilized and that both should decompose spontaneously into N3 radicals and N2. This conclusion was experimentally confirmed for the N5(+)N3(-) salt by low-temperature metathetical reactions between N5SbF6 and alkali metal azides in different solvents, resulting in violent reactions with spontaneous nitrogen evolution. It is emphasized that one needs to use adiabatic ionization potentials and electron affinities instead of vertical potentials and affinities for salt stability predictions when the formed radicals are not vibrationally stable. This is the case for the N5 radicals where the energy difference between vertical and adiabatic potentials amounts to about 100 kcal/mol per N5.     

Synthesis and characterization of the phosphorus triazides OP(N3)3 and SP(N3)3

Two explosive triazides of phosphorus(V), OP(N(3))(3) and SP(N(3))(3), have been prepared as neat substances and structurally characterized. Both compounds can be handled in gas, liquid, and solid states in submillimolar quantities. The melting points of OP(N(3))(3) and SP(N(3))(3) are +22 and -30 °C, respectively. The two triazides have been characterized by IR (Ar matrix and gas phase) and Raman (solid) spectroscopies. Their single-crystal structures were obtained by X-ray diffraction and found to be significantly distorted from the predicted ideal C(3) symmetry because of intermolecular interactions. The spectroscopic and structural properties are discussed in combination with density functional theory calculations.     

Synthesis of Nanocrystalline Zr3N4 and Hf3N4 Powders from Metal Dialkylamides

A simple process to synthesize Zr₃N₄ and nitrogen‐rich Hf₃N₄ powders via ammonolysis of metal dialkylamides, i.e. Zr(NEt₂)₄ and Hf(NEt₂)₄, at temperatures below 700 °C is presented. The obtained nitrides have a rhombohedrally distorted NaCl‐type structure, which has previously been reported only for nitrogen‐rich films of these nitrides. Regardless of the atmosphere (N₂ and He), the Zr₃N₄ starts to decompose above about ～ 650 °C and achieves the highest decomposition rate at about 900 °C, finally yielding the mononitride ZrN. Both Zr₃N₄ and Hf₃N₄ powders are nanocrystalline with the crystal size of about 2 nm.     

Ca3N2 and Mg3N2: unpredicted high-pressure behavior of binary nitrides

High-pressure synthesis allows both fundamental and materials science research to gain unprecedented insight into the inner nature of materials properties at extreme environment conditions. Here, we report on the high-pressure synthesis and characterization of γ-Ca(3)N(2) and the high-pressure behavior of Mg(3)N(2). Investigation of M(3)N(2) (M = Ca, Mg) at high-pressure has been quite challenging due to the high reactivity of these compounds. Ex situ experiments have been performed using a multianvil press at pressures from 8 to 18 GPa (1000-1200 °C). Additional in situ experiments from 0 to 6 GPa (at RT) at the multianvil press MAX 80 (HASYLAB, Beamline F.2.1, Hamburg) have been carried out. The new cubic high-pressure phase γ-Ca(3)N(2) with anti-Th(3)P(4) defect structure exhibits a significant increase in coordination numbers compared to α-Ca(3)N(2). Contrary, Mg(3)N(2) shows decomposition starting at surprisingly low pressures, thereby acting as a precursor for Mg nanoparticle formation with bcc structure. Soft X-ray spectroscopy in conjunction with first principles DFT calculations have been used to explore the electronic structure and show that γ-Ca(3)N(2) is a semiconductor with inherent nitrogen vacancies.     

Ab initio study of the spectroscopy of CH3N and CH3CH2N

Complete active space (CAS) calculations with 6-311++g(3df,3pd) basis sets were performed for a large number of electronic states of the nitrate free radical (CH3N/CH3CH2N) and their positive and negative ions. All calculated states are valence states, and their characters are discussed in detail. To investigate the Jahn-Teller effect on the CH3N radical, Cs symmetry was used for both CH3N and CH3CH2N in calculations. The results (CASPT2 adiabatic excitation energies and CASSI oscillator strengths) suggest that the calculated transitions of CH3N at 32172 and 32139 cm(-1) are attributed to the 2(3)A' ' --> 1(3)A' ' and 1(3)A' --> 1(3)A' ', respectively, which is in accordance with the A3E --> X3A2 emission spectrum at T0 = 31 817 cm(-1). The calculated transitions of CH3CH2N at 334 nm are attributed to the 1(3)A' ' --> 2(3)A' ' and 1(3)A' ' --> 1(3)A', respectively, which is in accordance with the UV absorption spectrum of a series of 11 bands beginning at 335 nm. The vertical and adiabatic ionization energies were obtained to compare with the PES data. These results are in agreement with previous experimental data, which is discussed in detail.